1. Field of the Invention
The present invention relates to a patterned anvil roll for pressing a continuously moving web to a second roll. The invention more particularly concerns an apparatus and method for ultrasonically bonding at least two continuously moving webs together using a rotary ultrasonic horn and a patterned anvil roll.
2. Description of the Related Art
Several different conventional methods have existed for pressing a continuously moving web between an anvil roll and another roll for the purpose of effecting a manipulation on the web such as, for example, bonding, cutting, embossing, perforating or chopping the web. For example, it has been well known to those skilled in the art to bond two continuously moving substrate webs together by constrictively passing them between a rotating bonding roll and a rotating anvil roll. The substrate webs have been bonded together by any means known to those skilled in the art such as thermal, ultrasonic or adhesive bonding. For example, the bonding roll has been heated to thermally bond the webs together as the webs constrictively traveled between the bonding roll and the anvil roll. Alternatively, the bonding roll has included a rotary ultrasonic horn which has been capable of transmitting ultrasonic energy to ultrasonically bond the two webs together as they constrictively traveled between the rotary ultrasonic horn and the anvil roll. Representative examples of rotary ultrasonic horns which have been used to bond at least two webs together are described in U.S. Pat No. 5,096,532 to Neuwirth et al. and U.S. Pat. No. 5,110,403 to Ehlert.
Typically, the bonding roll has had a smooth surface while the anvil roll has been configured with a bond pattern including a plurality of projections having bonding surfaces thereon and recesses therebetween to bond the webs together at the bonding surfaces in a predetermined pattern. Such a bonding roll has also been used to emboss, cut, perforate or chop the web or webs as well.
The consistency and quality of the bonds, cuts, embosses and the like and the resulting composite material can depend upon how well the material releases from the anvil and bonding rolls. For example, in many of the conventional patterned anvil rolls, the material momentarily sticks to the projections on the anvil roll which has undesirably resulted in tears in the material and inconsistency in the desired outcome such as inconsistent bonding, cutting, embossing, perforating, chopping and the like. This has been particularly true when the desired pattern includes very small dots or points or when one or more of the materials which are being passed between the rolls has included a coating thereon such as an adhesive. For example, when the pattern includes very small dots, the projections from the patterned anvil roll are much like pins which tend to snag and snare the materials being passed between the rolls. Moreover, when the materials include a coating such as adhesive thereon, the coating has often times filled the recesses between the projections on the anvil roll which has undesirably resulted in inconsistent bonds. Thus, conventional methods have not always been completely satisfactory.
The above-mentioned difficulties of maintaining the desired quality and consistency have been even more acute when ultrasonically bonding one or more continuously moving webs using a rotary ultrasonic horn. The rotary ultrasonic horn has inherent movement which may adversely affect the consistency and quality of the desired operation because it continuously vibrates at a given frequency and amplitude to efficiently bond, cut or emboss the web or webs. Moreover, in the case of coating buildup in the recesses between the projections on the anvil roll, such buildup has absorbed some of the ultrasonic energy generated by the rotary ultrasonic horn which has also undesirably resulted in reduced quality. Such acute difficulties have also been encountered when passing materials between an anvil roll and a rotary ultrasonic horn for other purposes including cutting, embossing, perforating, chopping and the like and combinations thereof. To improve the release of the material from the rolls, some conventional rolls have been coated with a nickel or chrome coating. However, such coatings have not been completely satisfactory. For example, such coatings have not always provided the desired snag free release of the material and reduced level of buildup in the recesses such as the undesirable buildup of adhesive.